Successful Firing of Sensitive Gemstones uisng Activated Carbon

Aqua Czs fired in Silver Metal Clay (using activated carbon to preserve colour)



Last week, I test fired the new gemstones that had arrived at BeadFx (posted o7/04/10). The one stone I was most excited about was an Aqua Cubic Zirconia which sadly failed my original kiln and torch firing tests. The stones turned brownish:

Left stone (brownish) is the result of (open) kiln firing aqua czs. Right stones are unfired aqua czs.

I was disappointed by I had one last test to try, which I did this week. Firing the piece in a kiln embedded in activated carbon, and guess what? I had success!!!!

Several weeks ago I posted about firing gemstone in metal clay (posted 06/20/10), in this post I referred to a great resource from Mardel Reins at Cools Tools - Gemstone Firing Guide. In this reference she mentioned that she came to the idea that perhaps it was the heat and oxygen that caused some gemstones to fail her test firings in metal clay. The advent of the new metal clays the require firing in an oxygen free environment (which is achieved by placing them in a pan covered in activated carbon) gave her the idea to test this theory with some of the failed gemstones. (you can read the full story on the link).

Thanks to this information I decided to try this on the new aqua czs. And this is what I did:

• I made a metal clay piece and embedded the aqua cz's in the metal clay.
• Dried it completely.
  
• Once completely dry. I used my butane torch to burn off the binder. I placed my piece on my kiln brick and ignited the piece (once the piece ignited, I turned off the torch, this is important as you don't want to overheat the piece and damage the stone).
  
• I repeated igniting the piece and then letting the flame go out until the piece did not flame any more. This was to burn off the binders.
  
• After all the binder was burned off I carefully placed the piece in a steel pan with activated carbon covering it completely.
  
• I fired it in my kiln at 1575F for 1.5 hours (the reason I didn't go higher was a time factor, in theory a higher temperature and longer will work as well).
• Cooled the piece naturally (remember you don't want to thermally shock your gemstones by quenching them).
  
• Polished.

Success the aqua colour was maintained!!!

Gemstone tests

As I mentioned in a previous post new gemstones arrived at BeadFx. When I add a new material that I am unsure of I will test fire it out of clay to make sure it can withstand the time and temperature I intend to fire it at.

I took six of the new gemstones and tested them at 1650F for 2 hours to see if they would withstand to maximum temperature I would fire my silver metal clay creations. Here are the results, the stones on the LEFT are the test stones that have been fired :

Garnet Cz (no obvious colour change)

Lab created black saphire (no obvious colour change)

Aqua Cz (Oh oh, BIG CHANGE -FAILED all my tests)

Lab created Blue Spinels (no obvious colour change)

Lab created Ruby (no obvious colour change)

Lavender Cz (no obvious colour change)


It looks like all but the AQUA cz's survived. I retested the aqua cz's at 1200F for 30 minutes (the minimum I would fire at) and they failed yet again, they turned a lighter yellow brown. I torch fired one for two minutes and yet again I got a shade of brown. Disappointing as this stone would look awesome embedded into silver, of course you could set it in a fine silver setting after firing. I will test them in carbon in the next few weeks.


Lastly, I had mentioned my tests with a piece of Labradorite at 1650F here is a picture of what happened:

Remember, if your fire gemstones in metal clay DO NOT quench them, allow them to cool naturally or you may cause thermal shock and the stone may fracture.

Testing new gemstones and others

If I am trying out a new material to add to metal clay, I will test fire it alone before I add it to my clay to see if it can withstand my normal firing temperature.

BeadFX just got in new gemstones and I have a sampling of six of them which I am test firing. The new stone that I am testing are:

• Garnet CZ (3mm round)
• Lab created Black Saphire (7mm round)
• Aqua CZ (3mm round) -this might be my favorite imagine it in silver
  
• Lab created blue Spinel (10mm heart)
• Lavender CZ (3mm)
• Lab created ruby (3mm)

I decide the the first test to subject them to is my maximum (the logic here is two things one according to some of the research I have made they should survive and the other point is if they all survive then no need to test them any further, thankfully I have extras if any fail)

The result of the first firing at 1650F for 2 hours (the stones on the LEFT are the ones that have been fired the stones on the RIGHT are the unfired samples) :

Garnet CZ (no obvious change in colour)



Lab created Black Saphire (no obvious change in colour)




Aqua CZ (Oh, Oh BIG CHANGE!!!)

Lavender CZ (no obvious change)

Lab created Blue Spinel (no obvious change)

Lab created Ruby (no obvious change)

After the first tests all but the aqua cz survived 1650F for 2 hours. Now I will have to retest aqua at a lower temperature. It seems that greens tend to be the least reliable colours so the fact that the aqua failed this test stands to reason . I will now test a new aqua cz at 1200F and see what happens.

Of note in my reading I have seen note that black saphires are not always consistent. I have had luck with these ones but it is interesting to note and it is only one test.

Lastly,

On my last post of adding gemstones I had made mention of my experiments with firing Labradorite at 1650F. Here is a picture of what happened:

I will update you on the successes or failures with the aqua CZ's.